Finding the Fourth Proportional to 1,420.78, 1,960.18 and 831.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.78 : 1,960.18 = 831.28 : x
2. Step 2: Convert to fraction form
   1,420.78/1,960.18 = 831.28/x
3. Step 3: Cross multiply
   1,420.78x = 1,960.18 × 831.28
4. Step 4: Simplify right side
   1,420.78x = 1,629,458.43
5. Step 5: Solve for x
   x = 1,629,458.43/1,420.78
6. Step 6: Final answer
   x = 1,146.88